Published Online
on August 25, 2009

A more recent version of this article appeared on October 1, 2009

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Original Article

Left Ventricular Septal and Left Ventricular Apical Pacing Chronically Maintain Cardiac Contractile Coordination, Pump Function and Efficiency

Robert W. Mills¹; Richard N. Cornelussen²; Lawrence J. Mulligan³; Marc Strik¹; Leonard M. Rademakers¹; Nicholas D. Skadsberg³; Arne van Hunnik¹; Marion Kuiper¹; Anniek Lampert¹; Tammo Delhaas¹ and Frits W. Prinzen^1,4

¹ Maastricht University, Maastricht, The Netherlands;
² Maastricht University & Medtronic, B.V., Maastricht, The Netherlands;
³ Medtronic, Inc. Minneapolis, MN

^* Corresponding author; email: frits.prinzen{at}fys.unimaas.nl

Background—Conventional right ventricular (RV) apex pacing can lead to adverse clinical outcome associated with asynchronous activation and reduced left ventricular (LV) pump function. We investigated to what extent alternate RV (septum) and LV (septum, apex) pacing sites improve LV electrical activation, mechanics, hemodynamic performance and efficiency over 4 months of pacing.

Methods and Results—After AV-nodal ablation, mongrel dogs were randomized to receive 16 weeks of VDD pacing at the RV apex, RV septum, LV apex, or LV septum (trans-ventricular septal approach). Electrical activation maps (combined epicardial contact and endocardial non-contact) showed that RV apical and RV septal pacing induced significantly greater electrical desynchronization than LV apical and LV septal pacing. RV apex and RV septal pacing also significantly increased mechanical dyssynchrony, discoordination (MRI tagging) and blood flow redistribution (microspheres) and reduced LV contractility, relaxation, and myocardial efficiency (stroke work / myocardial oxygen consumption). In contrast, LV apical and LV septal pacing did not significantly alter these parameters as compared to the values during intrinsic conduction. At 16 weeks, acute intra-subject comparison showed that single site LV apical and LV septal pacing generally resulted in similar or better contractility, relaxation and efficiency as compared to acute biventricular pacing.

Conclusions—Acute and chronic LV apical and LV septal pacing maintain regional cardiac mechanics, contractility, relaxation and efficiency near native levels, whereas RV apical or RV septal pacing diminish these variables. Acutely, LV apical and LV septal pacing tend to maintain or improve contractility and efficiency compared to biventricular pacing.

Key Words: hemodynamics • mapping • mechanics • oxygen • pacing